I have a 1973 Johnson 6HP (6R-73S J3729766) which I just got running after two months. It had been used in saltwater previously and while changing the head gasket and impeller I found lots of caked salt and calcium blocking passages. The wet salt looked like it might have been from sitting for two months, but the caked calcium looked like it has been building for 30 years. The engine is running fine now and the exhaust cover feels cool while running, but I'm wondering if I should pull the exhaust cover and clean out that area as well.<br /><br />The lower screws look to be very difficult (although not impossible) to access without removing the power head. The manual also makes it sound like breaking those screws is commonplace -- I guess they aren't as beefy as the head cover screws.<br /><br />Is changing the exhaust gaskets and cleaning out the area normal preventative maintenance? (I'm sure it's never been done since the head gasket was original). How difficult is it to remove the exhaust cover on this model? Does the exhaust contain small passages that are likely to be blocked by salt & mineral deposits like I saw in the head and impeller areas? If it's running fairly cool should I just leave well enough alone?<br /><br />I also wonder if there's some product I can use in my flush bucket to help clean out these deposits without dissassembling the engine. Boiling water did wonders on some of the head cover deposits, although a lot of it was only removeable by a screwdriver.
